INPP5A and cancer: Intracellular IP3 levels are controlled in part by inositol phosphatases such as the ubiquitously expressed plasma membrane-associated31 inositol 5-phosphatase INPP5A, which specifically hydrolyzes IP3 (and IP4) to repress calcium signaling32 and is downregulated in cancer and spinocerebellar ataxia type 1733–37.